1. Field of the Invention
The present invention relates to a valve timing control device to be used for controlling the opening/closing timing of an intake valve or an exhaust valve in a valve actuating mechanism of an internal combustion engine.
2. Description of the Related Art
In Unexamined Published Japanese Patent Application No. 1-92504 or Unexamined Published Japanese Utility Model Application No. 2-50105, for example, there is disclosed a valve timing control device of that kind, comprising a rotation transmitting member so mounted around a valve opening/closing rotary shaft (including a cam shaft and an internal rotor integrally mounted on the cam shaft) rotatably assembled with the cylinder head of an internal combustion engine so as to rotate relative thereto within a predetermined range for transmitting a rotating power from a crank shaft; vanes provided on the rotary shaft; a fluid chamber formed between the rotary shaft and the rotation transmitting member and halved into advancing chambers and delaying chambers by the vanes; first fluid passages for feeding and discharging a fluid to and from the advancing chambers; second fluid passages for feeding and discharging the fluid to and from the delaying chambers; a refuge hole formed in the rotation transmitting member and accommodating therein a lock pin spring-biased toward the rotary shaft; a fitting hole formed in the rotary shaft for fitting therein the head portion of the lock pin when the rotary shaft and the rotation transmitting member are synchronized in predetermined relative phases; and a third passage for feeding and discharging the fluid to and from the fitting hole.
The valve timing control device, as described in each of the above-cited patent applications is constructed such that the lock pin is moved against the spring-urging force by the pressure fluid fed to the fitting hole via the third fluid passage thereby to release the locking by the lock pin. The valve timing control device is also constructed such that the feed and discharge of the fluid to and from the third fluid passage are effected simultaneously with the feed and discharge of the fluid to and from the first fluid passage and the second fluid passage. As a result, the displacement transformation (or the relative rotations of the rotary shaft and the rotation transmitting member) may be started prior to the unlocking by the movement of the lock pin. In this case, excessive friction occurs between the lock pin and the fitting hole so that the unlocking by the movement of the lock pin may not be properly effected.